I have been doing P90X for a few weeks now. It seems to be effective and it doesn't require a lot of equipment other than bands/freeweights and a pull-up bar. I use weights from 5 to 25 lbs but could use some heavier weight for some of the back exercises.

I use the Perfect Pushup in my circuit training and it is one of the most brutal exercises I have ever done. It feels like someone is screwing 6" screws into my chest. The pain is worth the results however.

I was getting too many overuse injuries with weights so I turned to Insanity only for 60 days with no weights(there may be some). So far it's intense, gets you sweating and burns calories with crazy exercises and pilates/yoga stretching. The only problem is you can easily walk away from the tv to the refrigerator. You have to push yourself, eat your meals(5 per day at 3-400 calories each) which prevents snacking. I like it so far and I am just about finished week 2.

i purchased The Firm's Transfirmer system. i liked it pretty well, but i really really like the newer videos with the pink covers. now i have 4 tapes and they are awesome. they require 3 sets of weights, lite, medium, and heavy. i use 3,5, & 8 lb dumbells. check them out.